Systems and methods for activating thermochromic ink labels

ABSTRACT

In methods and systems for activating a label including a thermochromic ink used as a time/temperature indicator, the label has a first or printing section, and a second or thermochromic ink section. A package parameter, such as the weight of a food package or portion, is determined and printed on the printing section of the label. The label is advanced to an activation energy station. At least the thermochromic ink section of the label is exposed to activation energy, such as heat or radiation. The label is then quickly moved to a cooling station. At the cooling station, at least the thermochromic ink section of the label is quickly cooled, to activate the label for use as a time/temperature indicator.

BACKGROUND OF THE INVENTION

The field of the invention is activation of labels using thermochromic ink as a time/temperature indicator.

Time/temperature indicators are commonly used on perishable products, typically food products that require refrigeration to maintain product quality. Although various types of time/temperature indicators have been used, they all generally are designed to provide an indication that the indicator has been exposed to a temperature above a specified temperature, for more than a specified period of time. For example, a time/temperature indicator on a perishable dairy product such as pasteurized milk may change color, or undergo another form of visual change, if exposed to a temperature above 5° C. (40° F.) for more than four hours.

One type of time/temperature indicator uses an activated thermochromic material, such as thermochromic ink. Thermochromic inks change color in response to temperature changes. In use for a time/temperature indicator, the ink may be printed on a label that is applied to or wrapped around a specific perishable food item. When the temperature of the label exceeds a given value, the thermochromic ink in a typical case darkens noticeably. The darkening provides a visible indication that the product may have been exposed to higher temperatures than is appropriate. Some thermochromic inks must be activated after they are printed onto a label to be used as a time/temperature indicator. Activation is achieved by first exposing the thermochromic ink on the label either to an intense light source or high heat, and then followed by quickly cooling the thermochromic ink to a very low temperature. After activation is achieved, the thermochromic ink will retain its initial color and remain stable or “untripped”, unless exposed to a temperature above a “trip” temperature, for a sufficient amount of time. The trip temperature is selected based on the particular temperature requirements of the product that the thermochromic label is used on, and is achieved via the chemical composition of the ink. These characteristics of thermochromic materials are well known, as described for example in International Patent Application No. PCT/US2003/020537, incorporated herein by reference.

In view of the requirements for activation for thermochromic inks as described above, engineering challenges remain in designing systems and methods for effectively performing activation. It is an object of the invention to provide improved systems and methods for achieving activation of thermochromic ink labels.

SUMMARY OF THE INVENTION

In a first aspect of the invention, a label may include a thermochromic ink section and a conventional printing area. A package parameter, such as the weight of a food package or portion is determined and can be printed in the conventional printing area. This printing can be accomplished in various ways, including direct thermal printing. After the conventional printing is completed, at least the thermochromic ink section of the label is exposed first to an activation energy source, such as intense light or high heat. The label is then quickly moved to a cooling station. At the cooling station, at least the thermochromic ink section of the label is quickly cooled to a very low temperature. Where heat is used as the activation energy, the label temperature is typically at least 100° C. The cooling station typically brings the label to a temperature below 0° C. The activation energy source may activate the thermochromic ink with or without substantial heating of the label.

In a second aspect of the invention, as applied to food products, a food package labeling system for refrigerated or frozen foods includes a scale and a label printer for printing a weight as measured by the scale on a label. A thermochromic ink label activator in the system includes a first stage activation energy source and a second stage rapid label cooling unit. The system also includes a label transport system for moving a sequence or strip of the labels through the label printer and thermal label activator. The labels may have a first area for printing by the label printer, and a second area containing a thermochromic ink which is activated by the thermal label activator. The first stage activation energy source may include a may include a radiant illumination unit, such as a UV or IR lamp. It may also instead include a contact hot plate or hot air source to help cause rapid absorption of energy into the thermochromic ink part of the label. The rapid cooling unit may include a cold plate moving into momentary physical contact with the second area of the label.

The methods and systems of the invention provide for improved thermochromic ink label activation. Other and further objects and advantages will become apparent from the following detailed description of the invention. This description provides examples of embodiments of the invention and is not intended to be understood as defining the limits of the scope of invention. Rather, the scope of the invention is set forth in the claims, and their equivalents, following the detailed description, and in the detailed description itself.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, the same element number indicates the same element in each of the views.

FIG. 1 is a schematic view of the present labeling system.

FIG. 2 is a schematic side view of the thermal activation unit shown in FIG. 1.

FIG. 3 is a schematic side view of an alternative labeling system.

FIG. 4 is a schematic side view of another alternative labeling system.

FIG. 5 is a flow chart showing a label activation process.

FIG. 6 is an enlarged view of a label that may be activated using the systems and methods described.

DETAILED DESCRIPTION OF THE DRAWINGS

Turning now in detail to the drawings, as shown in FIG. 1, a labeling system 10 includes a printer 16 and a thermochromic ink activator unit 20. These and other system components may be contained within an enclosure or housing 12. The system 10 may also include a scale 22 and a keyboard/monitor 24, or other user interface and controller. The printer 16 is electrically linked to the scale 22. As food portions or packages are placed on the scale 22, the printer 16 prints the package weight on a printing section of a label 34. The printer 16 may use conventional ink on paper printing techniques.

In the design shown in FIG. 1, labels 34 are provided on backing strip or tape 32 on a spool 14. FIG. 6 shows an enlarged view of a label 34. The printer 16 prints on a printing section 114 of the label 34. The printer 16 may be a direct thermal printer using temperatures over 150° C. The label also has a trans-informational section 110A including a thermochromic ink. Additional details on the physical characteristics of the label are provided in U.S. Pat. No. 7,157,048, incorporated herein by reference.

Referring still to FIG. 1, a label drive system 18 moves the strip 32 through or past the printer 16 and the activator unit 20. The activator unit 20 includes a first stage activation subsystem 38 and a cooler 50. As shown in FIG. 2, the first stage activation system may include a radiant lamp 40 and a reflector 42 to energize a label 34 positioned at a first or activation energy station. One or more lenses 44 may optionally be used. The lamp 40 may be a linear UV lamp. Various other types of radiant light illumination systems may alternatively be used. Conductive and convective heaters, and combinations of radiant light illumination systems, plus conductive and convective heating, may also be used. Radiant light illumination system are advantageous as they do not require any moving parts and can be calibrated to provide uniform and precise energizing of the label as the first stage of activation. They also do not require physical contact with the label, which can cause inadvertent displacement of the thermochromic ink on the label. Direct thermal printing may used for the conventional printing, and the first stage of label activation for the thermochromic ink designed for this process and may be activated at slightly over about 100°C. Then because the activation temperatures used are lower than the temperature required to print with direct thermal printing, the first stage of activation does not damage the printed information on the label, even if the printed information is exposed to the first stage of activation.

In the particular design shown in FIG. 2, the cooling unit 50 includes a thermoelectric cooler 56 having a cold plate 54 associated with a cooling station 60. An exhaust fan 58 removes heat from the thermo-electric cooler 56, in a direction away from the cold plate 54. A cold plate actuator 62 moves the cold plate 54 into and out of contact with an activated label 34 moving into the cooling station 60 from the activation energy station 46. A pressure pad 52 may optionally be aligned with the cold plate 54. Of course, various other equivalent types of cooling units and cooling techniques may be used. A de-icer 70 may be used to avoid build up of ice on the cold plate, so that the cold plate 54 remains efficient in cooling labels 34 during operation of the labeling system. The de-icer 70 may use various known techniques for removing ice, including heating, chemical removal, or physical removal using moving mechanical elements and/or streams of liquids or gases.

Referring to FIGS. 1 and 2, the labels 34 may have an adhesive back and be provided on the label strip 32, with a small uniform gap between each adjacent label. The label strip 32 extends through the printer 16 and the thermal activator unit 20. Alignment guides 35 may optionally be used to keep the label strip 32 properly aligned and positioned within the printer 16 and the activator 20. However, in most designs operating with a label strip, alignment guides are generally not needed. As shown in FIG. 2, a base plate 30 may extend at least through the activator 20, to support the label strip 32 vertically, while the alignment guides 35 (if used) support or guide the label strip 32 laterally. The label drive system 18 pulls the label strip 32 from the spool 14, through the printer 16 and the activator 20, typically in uniform steps to sequence labels 34 on the label strip 32 through the labeling system 10. The label drive system 18 may advance the label strip 32 via pinch rollers 18, reciprocating elements, or similar designs. The label drive system may be set up to contact only the edges of the label strip 32, so as not to contact the labels themselves.

In operation, the labeling system 10, in a typical setup, may be located in the meat or fish department of a supermarket or similar retail store. The system operator uses the keyboard, control panel or other interface 24 to turn the system 10 on, and optionally to check that the system 10 is ready for operation. These checks may include indications that a sufficient label strip 32 is loaded onto the spool 14, and that the system components such as the scale 22, printer 16 and activator 20 are ready for operation. One or more test labels may optionally be printed and activated.

The user places a food portion or package on the scale 22. The scale 22 may optionally be separate and remote from the labeling system 10, depending on the setup and work flow. The weight of the food portion or package as measured by the scale is provided to the printer 16 as an electrical signal. The scale 16 prints the weight onto a label. The scale may optionally print additional information as well, such as price per pound, time, date, store number, etc. The food portion may be placed into a tray, such as a Styrofoam tray or other single use support. The food portion may also be wrapped, or unwrapped, when weighed. After the weight is printed on the label 34, the drive system 18 is momentarily actuated to move the printed label from the printer 16 to the activation energy station 46. During this movement, a following adjacent label on the label strip 32 moves into the printer 16.

The first stage activation system 38 may generally operate at a steady state. Regardless of whether a radiant illumination source or a convection or contact heat source is used to energize the label at this stage, it is helpful to have the heat source or the lamp 40 left on when the system 10 is in constant use. As a result, energy absorption at the activation energy station 46 is consistent, based on the design of the activation system components, which may include a specific lamp and optics or specific heating element devices. If the system 10 is in intermittent use, the activation energy station 46 may switch on and on according to various timing sequences, as controlled or programmed by the controller 25. The on/off operation of the first stage activation system may also be linked to the operation of the printer 16, since operation of the printer 16 precedes operation of the first stage activation system 38.

FIG. 5 shows the steps associated with the activator unit 20. At step 80, a label 34 on the strip 32 is positioned to move into the printer 16. This step may be achieved via the use of the alignment guides 35 and the base plate 30. Alternatively, some types of label strips 32 may feed directly from a spool 14 (or other bulk label storage element) into the printer 16. At step 82, the label 34 moves into the printer 16. The printer 16 prints the food weight and/or other information on the printing section 114 of the label 34. The printed information may be generated by the scale and/or the keyboard 24 or electronic controller 25. The drive system 18 then incrementally advances the label strip 32, moving the now printed label 34 into the activation energy station 46. Next, at step 86, in the activation energy station or system 46, either exposure to high radiant energy or high heat is applied to the label 34. If direct heat is used at this stage, the label 34 may be heated to an elevated temperature, typically a temperature of between 80 and 150° C. and for a period of between 0.5 and 4 seconds. High energy absorption at this first stage of activation causes the molecules of the thermochromic ink to change shape and unfold. This changes the optical properties of the ink. The precise temperatures and/or illumination exposure requirements at this energy activation stage or step will vary with the type of thermochromic ink used, and may be obtained from the ink manufacturer, or determined empirically.

After the activation energy step 86, the drive system 18 again incrementally advances the label strip to move the label 34 into the cooling station 60. When the thermochromic ink is no longer exposed to the activation energy source, it tends to revert to its original state. To prevent this reversion, and to preserve the utility of the label 34 as a time/temperature indicator, the label is quickly cooled at the cooling station, at step 90. This step is performed by cooling the label 34 to a typical temperature of from −5 to −25° C. or −10 to −20° C. for 1, 2, 3, 4 or 5 seconds. This cooling completes the activation of the thermochromic ink on the label 34. Colder temperatures and longer cooling times may be used, but generally are not necessary. At step 92 in FIG. 5, the drive system 18 again advances the label strip 32 moving the now fully activated label out of the activator unit 20.

To achieve rapid cooling of the label 34, the cooler 50 including the cold plate 54 may be used. In this case, the cold plate actuator 62, optionally controlled by the controller 25, quickly moves into contact with the activation area 110 on the label 34. The label 34 is lightly pressed between the cold plate 54 and an underlying supporting surface, such as the pressure pad 52 of a base plate 30. To reduce the time delay between exposure to the activation energy source and cooling, the label drive system 18 may advance the label strip quickly, so that movement of the label into the cooling station 60 takes less than 1, 0.5 or 0.3 seconds.

The cooling station 60 may also be adjacent to the activation energy station 46, to reduce the time required for movement of the label into the cooling station. The minimum spacing between the activation energy station 46 and the cooling station 60 will depend in part on the size of the labels 34. Typical labels are about 5-14 cm (2-5 inches) long (dimension L in FIG. 6) and 5-9 cm (2-3.5 inches) wide. The strip 32 may be 2-10 cm wider than the label 34. With 8 cm×8 cm labels, the centers of the activation energy station and the cooling station may be less than 16, 12, or 10 cm apart. The activation area or field 100 of the label 34 is generally at least 5 cm wide and 2 cm long. The activation energy station 46 and the cooling station 60 may be dimensioned based on the activation area. While the labels 34 are generally adhesive back paper labels, labels of other materials, such as plastic, may also be used.

After weighing, the food package is wrapped (unless it has already been wrapped before weighing). Wrapping may be done manually by the operator or automatically via a wrapper or packager 26 associated with the labeling system 10. The now activated label is applied to the food package. This may be done manually by the operator or automatically by a label applicator 28.

The activated label is temperature sensitive. If the label is exposed to a temperature above a selected trip temperature, the thermochromic ink layers on the label will begin to darken or “trip”. The trip temperature is determined by the make up of the thermochromic ink. A typical trip temperature is 4° C. (40° F.). This trip temperature is useful for many perishable food products that require refrigeration. The activated label will remain stable and un-tripped for virtually as long as it remains at 4° C., or lower. If exposed to temperatures over about 4° C. for a sufficient trip time period (usually several hours), the label will trip as the thermochromic layers of the label permanently darken. The darkened label provides a visual indication that the food product has been exposed to too high a temperature for too long of a time during some point in its handling and storage, prior to reaching the point-of-sale, or some other interim scanning or inspection point.

Too avoid initiation of tripping the labels immediately after they are activated, the labeling system may be located in an environment at 4° C. or less. For use on frozen foods, the labels 34 have a trip temperature of 0° C. or less. Other trip temperatures may be used for other types of products, such as medical products including pharmaceuticals, blood and organs, vaccines, live organisms, etc. Activated labels may also be used on chemical products, such as paint. In addition to placing labels 34 onto food, beverage, wine and candy packages or containers, activated labels may be used on raw materials, shipping containers, and the packaging or containers of various temperature sensitive products.

FIG. 3 shows an alternative design similar to the system 10 shown in FIGS. 1-2, but operating with individual labels moved on a conveyor belt 36. In this design, labels may be placed manually onto the conveyor for movement to the activation energy station 46 and the cooling station 60. Since unlike the system 10 shown in FIGS. 1-2, the labels are not on a label strip 32, guides 35 are used to keep the labels properly aligned.

FIG. 4 shows another alternative design similar to the system 10, but with two coolers 50 positioned on opposite sides of the label 34. In this design, upper and lower (or left and right) cooling plates 54 move against upper and lower surfaces of the label. Faster cooling may be achieved by cooling both sides of the label simultaneously. Optionally, either one of the two cooling plates shown in FIG. 4 may be fixed in place, essentially forming a cooling base plate 30. As shown in FIG. 4, a similar concept may be used for exposing the label to activation energy, such as UV or IR radiation, or to thermal heating. In FIG. 4, a first activation energy source or heater 38, shown in solid lines, exposes or heats a first side of the label. If desired, a second activation energy source or heater, shown in dotted lines, may be used to expose or heat the second side of the label. However, as the labels are less sensitive to heating times than to cooling times, usually a single activation energy source 38 will be sufficient.

Thus, a novel labeling system and thermal label activator have been shown and described. Various changes and substitutions may of course be made without departing from the spirit and scope of the invention. The invention, therefore, should not be limited, except by the following claims and their equivalents. 

1. A food package labeling system for refrigerated or frozen foods, comprising: a scale; a label printer electrically linked to the scale; a label activator for activating a food package label, the activator including an activation energy unit and a rapid label cooling unit; and a label transport system for moving a sequence of labels containing thermochromic ink through the label printer and label activator.
 2. The labeling system of claim 1 further comprising a strip of labels on a spool, and with the label transport system comprising contact elements that contact the strip of labels as the strip exits from the thermal label activator.
 3. The labeling system of claim 1 further comprising an automatic food package wrapper adapted for wrapping a food package after the food package is weighed on the scale.
 4. The labeling system of claim 1 further comprising a label applicator adapted to attach an activated food label onto a food package.
 5. The labeling system of claim 1 with the activation energy unit comprising a radiant heater, a UV light source, and/or an IR light source.
 6. The labeling system of claim 1 with the cooling unit having a cold plate and an actuator for moving the cold plate into contact with label.
 7. The labeling system of claim 6 further comprising a flexible pressure pad associated with the cold plate.
 8. The labeling system of claim 1 with the label transport system comprising a conveyor belt.
 9. A food package labeling system for refrigerated or frozen foods, comprising: a label printer; a label activator for activating a food package label, the activator including an activation energy station having a radiant energy source, with the label provided on a strip of labels and the label containing a thermochromic element, the radiant energy source fixed in position relative to the activation energy station, and the label activator also including a cooling station adjacent to the activation energy station, a cold plate associated with the cooling station, and an actuator for moving the cold plate and the label together into physical contact with each other at the cooling station; and a label strip transport system for moving the strip of labels through the label printer and label activator.
 10. The food packaging labeling system of claim 9 with the activation energy station having a first dimension in the direction of movement of the strip, and with the cooling station having a second dimension in the direction of movement of the strip, and with the activation energy station spaced apart from the cooling station in the direction of movement of the strip by a dimension less than the first dimension and less than the second dimension.
 11. The food packaging system of claim 9 with the activation energy station continuous with the cooling station.
 12. The food packaging system of claim 9 further comprising a scale for weighing food, with the scale electrically linked to the label printer.
 13. A method of labeling food packages, comprising: providing a label including a thermochromic ink section and a printing section; determining a food parameter; printing the food parameter on the printing section of the label; exposing at least the thermochromic ink section of the label to activation energy at an activation energy station; moving the label to a cooling station; cooling the label at the cooling station to a temperature below 0° C., within 3 seconds from the time that movement of the label from activation energy station begins.
 14. The method of claim 13 wherein the label is cooled at the cooling station to a temperature below −15° C. within 3 seconds from the time that movement of the label from the activation energy station begins.
 15. The method of claim 13 wherein the exposing step comprises heating the label.
 16. The method of claim 15 further comprising heating the label to a temperature above 100° C.
 17. The method of claim 13 wherein the exposing step comprises exposing the label to radiant energy.
 18. The method of claim 17 wherein the radiant energy comprises UV or IR light.
 19. The method of claim 13 further comprising printing the food parameter via direct thermal printing.
 20. The method of claim 13 further comprising cooling the label via a spray of a cooling medium.
 21. The method of claim 21 wherein the cooling medium comprises a cooling gas.
 22. The method of claim 21 wherein the cooling gas comprises liquid nitrogen or cooled air.
 23. The method of claim 13 wherein the label is cooled at the cooling station to a temperature below −15° C. within 1 second from the time that movement of the label from the heating station begins.
 24. The method of claim 13 wherein the food parameter is weight, and the food parameter is determined by weighing the food.
 25. The method of claim 13 wherein the cooling is performed by contacting the thermochromic ink section of the label with a cold plate.
 26. The method of claim 25 wherein the cooling is performed by pressing the thermochromic ink section of the label between the cold plate and a pressure surface.
 27. The method of claim 26 further comprising de-icing at least one of the cold plate and the pressure surface by applying heat.
 28. A method of labeling food packages, comprising: providing a label including a thermochromic ink section and a printing section; determining a food parameter; printing the food parameter on the printing section of the label; heating at least the thermochromic ink section of the label to a temperature of greater than 100° C. at a heating station; moving the heated label to a cooling station; cooling the heated label at the cooling station to a temperature below 0° C., within 3 seconds from the time that movement of the label from heating station begins.
 29. The method of claim 28 wherein the heated label is cooled at the cooling station to a temperature below −15° C. within 3 seconds from the time that movement of the label from the heating station begins. 